Voice-based, turn-by-turn GPS navigation on the iPhone won't steer you wrong. But, no matter how good the program and the phone — even the iPhone — it's still a phone and not a dedicated GPS device.

TomTom, among the GPS giants worldwide, recently released its navigation program for the iPhone. After some initial crashing — on the phone, that is — I found it to be a solid, easy-to-use program, although pricey at $99.99. If you have the program for even, say, a year, it would cost about $8.50 a month. Still, other GPS phone programs run about $10 a month.

What we don't know is how much TomTom will charge for its iPhone car kit, which is not only a mount for the phone, but includes a GPS receiver, iPhone power supply, speaker and microphone for hands-free calling. Nor do we know when it will be out, or what the cost will be for software updates about road changes.

"It’s still too early to reveal any specifics on this now," a TomTom spokesman said. "We will announce more details in a forthcoming press release."

So before reading on, you may decide right here to hold off on TomTom for the iPhone until that kind of information is available.

Only recently available on iPhone
While many smartphones and feature phones can handle voice-based, turn-by-turn navigation, it has been something that was lacking in the iPhone since last year, when the 3G model with a GPS chip in it came out.

Apple's June release of the iPhone's 3.0 operating system software made such programs possible, and TomTom's has been highly anticipated. Research firm Strategy Analytics recently said that worldwide GPS smartphone shipments are expected to increase 34 percent, from 57 million units in 2008, to 77 million units this year.

But, just as using Wi-Fi on a smartphone or downloading honking video files drains the battery very quickly, so does GPS. That's why you'll at least want to have a car phone charger on hand at all times with any navigation program on a phone.

I tried out the TomTom program without plugging the iPhone into the car charger, just to see how battery life was without any help. It was not pretty. I drove a 20 miles for 45-minutes round trip, starting out with a nearly full battery, and watched the battery icon descend to about a half full.

"The iPhone 3G (and 3GS) has a built-in GPS receiver, but the performance that people would experience with the car kit is enhanced, and is probably much more comparable to one they would get in a dedicated portable navigation device," Tom Murray, vice president of market development for TomTom, told me
a few months ago
when TomTom for iPhone was first announced.

But, he'd said, "Once you download the application, you'll be able to take advantage of navigation immediately, and then you're off and running,"

A little underpowered
And I found that to be true. Yet as good as the TomTom's offering is — and it is — it feels a little underpowered on the iPhone. I'm not sure whether that's because of the terrain around me, the phone, the GPS chip in it or because voice-based navigation on phones is not optimal.

When I say "underpowered," I mean issues like this: Getting a message saying I'm in an area where there's "Poor GPS Reception" or no GPS reception, and seeing the color screen go gray in dismay in the middle of navigation, or despite the volume being cranked up, not being able to hear directions well enough.

TomTom

TomTom's car kit for the iPhone will have a GPS receiver and speaker. No word yet on the pricing of the kit.

Of course, you can modify the latter by using the car's speakers. I was just rolling using the "download the program and be off and running" model.

I tested it out on a 16-gigabyte 3G iPhone, with plenty of room for the 1.2-gigabyte TomTom software. The 3G phone, which came out in 2008, has a GPS chip in it, as does the newer and faster 3GS, released in June.

Is there any difference between the GPS chips? An Apple spokesman said that's "not something we specify."

Avi Greengart, consumer devices research director for Current Analysis, said Apple "has not revealed any information on the chipsets it is using, and made no claims that the GPS in the iPhone 3GS is superior in any way — at least none that I am aware of."

However, he said, the iPhone 3GS "does have a significantly faster processor, and that may affect how well navigation applications run; they’ll certainly load faster on the newer phone."

Another point in favor of a car kit or separate mount when using GPS on any phone is that it will place the phone closer to the windshield to help improve the signal reception from Global Positioning System satellites.

I used the program with a passenger in the car to hold the phone and really watch the screen, and I also used it while driving alone, relying on the voice to guide me. And yes, it's tempting to look — and extremely dangerous — at the screen when driving, all the more reason to make sure you can really hear the directions being given if you are driving alone.

Rerouting, but no text-to-speechI was really pleased with the program's responsive "rerouting" feature, where the navigation tells you to go one way, and you either pass that turn, or take a different route and it recalculates where you need to go based on which way you did turn. It worked very quickly, which is what you want when you're behind the wheel.

There is no text-to-speech feature. TomTom's voice guidance says "Turn right," and not "Turn right on Broadway," so that the program is not translating the actual text of the directions into speech. It would be more helpful — and less monotonous — to have that feature.

"As with all our products, we will continue to look at incorporating new innovations and technology for the app over time," said Kevin Carter of TomTom, when asked about text-to-speech.

TomTom uses its "IQ Routes" technology on the iPhone program. IQ Routes calculates the fastest route available, based on the experiences of TomTom drivers, the company says, helping drivers "reach their destination up to 35 percent of the time." Alternate route options are also available for avoiding roadblocks and toll roads.

There's also day-and-night modes and portrait-and-landscape modes for the screen.

Other programs
TomTom wasn't quite the first out with voice-based, turn-by-turn navigation for the iPhone, but it is the best-known of the companies offering it so far.

Navigon

Navigon's GPS navigation program for iPhone features 3-D views of the road.

Navigon came out with its MobileNavigator for iPhone in late July. The program costs $69.99 through Aug. 31; after that, the price will be the same as TomTom's.

Among MobileNavigator's features are "Reality View Pro," which shows 3-D views with road signs and lane guidance, as well as "Lane Assistant Pro," which the company says helps drivers "prepare to make an upcoming exit or turn by providing a lane map complete with arrows and actual road geometry."

There's also a "Speed Assistant" that provides an audio and visual warning.

MobileNavigator, like TomTom, also has day-and-night modes, as well as portrait-and-landscape views for the phone screen.

AT&T, the exclusive carrier of the iPhone in the United States, started offering a voice-based program, AT&T Navigator for iPhone, in June. It costs $9.99 a month. (You can try it out for free for 30 days on AT&T's other phones, but not on the iPhone.)

The carrier's program, also offered on many of its other phones, uses TeleNav's software.

(TeleNav also recently introduced its voice-based TeleNav GPS Navigator service for the new Google phone, the T-Mobile myTouch 3G. A free 30-day trial of the software is available; the program costs $9.99 a month.)